Ponyo found itself struggling to get to first place in it opening day as the 11th Pocket Monsters film Diamond & Pearl: Giratina and the Sky's Bouquet: Shaymin opened on the same day in Japan. Shaymin took in a respectable $7.3 million and was second in the Saturday box office sales behind Ponyo which raked in $8.2 million.
Ponyo was also released on July 19 on 481 screens and was expected to dominate while Pocket Monsters opened on 359 screens.
Sources:
http://www.cinematical.com/http://eiga.com/ranking/